Green Tea Extract benefit, dosage, research studies, supplement information

Green tea extract in the form of supplements has become quite popular and research suggests green tea extract has many health benefits. This web page will review the studies regarding the benefits and side effects of green tea extract.

Green tea extract benefit
Antioxidant benefit
Weight loss benefit, particularly if green tea is combined with other natural diet herbs and nutrients.
Anti cancer potential

Green Tea Extract, 100 mg, yielding 35 mg EGCG

Green Tea Extract offers a convenient way to get the benefits of green tea in a highly concentrated green tea pill form.  This green tea extract is standardized for bioflavonoid-like antioxidants known as polyphenols, particularly Epigallocatechin Gallate EGCG. EGCG has been found in scientific studies to be a potent antioxidant. Green tea antioxidants are likely to become more popular with time.

Green Tea Supplement Facts
Green Tea Extract Yielding 35 mg epigallocatechin gallate EGCG

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Green tea extract increases antioxidant and detoxification enzyme levels
Green tea extract capsules, when given to humans, increase the production of glutathione S-transferase enzymes which are helpful in detoxification and cancer prevention. Dr. H.-H. Sherry Chow, of the University of Arizona, Tucson, gave volunteers four green tea extract capsules, each containing 200 mg of epigallocatechin gallate, every morning prior to eating. This provided the equivalent amount of epigallocatechin gallate obtained from drinking 8 to 16 cups of green tea daily. Those with the lowest GST levels at the start of the study and who took the green tea extracts were found to have glutathione S-transferase (GST) enzymes increased by 80 percent. Those who had good levels of glutathione S-transferase did not have much of a change in their levels. Cancer Epidemiology, Biomarkers and Prevention, August 2007.
   Comments: We don't think there is a need to take this high a dosage of green tea extract. Drinking one or two cups a day or taking one tablet of a green tea extract a few times a week should be fine. Most people are also taking other antioxidant supplements, and too much green tea can cause shallow sleep.

Green teat extract benefit during hemodialysis
Supplementation with decaffeinated green tea extract ( catechins ) has beneficial effects on hemodialysis-induced reactive oxygen species, atherosclerotic disease risk factors, and proinflammatory cytokines. Green tea extract catechins reduce hemodialysis-induced production of hydrogen peroxide and hypochlorous acid, atherosclerotic disease risk factors, and reduce inflammation.

Does green tea extract lower blood sugar?
It does not appear that green tea has much of an influence on blood sugar levels. However, this does not mean it is not beneficial to those with diabetes. Since green tea extract has has potent polyphenol antioxidants, drinking green tea or taking a green tea extract may be helpful in terms of overall antioxidant status in the body. Furthermore, as you can see from the study listed below, green tea extract may reduce collagen cross linking.

The effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus: double-blind randomized study.
Metabolism. 2007 Oct;56(10):1340-4. Mackenzie T, Leary L, Brooks WB. Department of Community and Family Medicine, Dartmouth Medical School, Hanover, NH 03755, USA; Department of Medicine, Dartmouth Medical School, Hanover, NH 03755, USA; Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
Recent evidence suggests that tea from Camellia sinensis (eg, green, oolong, and black tea) may have a hypoglycemic effect. We evaluated the ability of an extract of green and black tea to improve glucose control over a 3-month period. A double-blind, placebo-controlled, randomized multiple-dose (0, 375, or 750 mg per day for 3 months) study in adults with type 2 diabetes mellitus not taking insulin was performed. The primary end point was change in glycosylated hemoglobin at 3 months. The 49 subjects who completed this study were predominantly white with an average age of 65 years and a median duration of diabetes of 6 years, and 80% of them reported using hypoglycemic medication. After 3 months, the mean changes in glycosylated hemoglobin were +0.4, +0.3, and +0.5 in the placebo, 375-mg, and 750-mg arms, respectively. The changes were not significantly different between study arms. We did not find a hypoglycemic effect of extract of green and black tea in adults with type 2 diabetes mellitus.

Effect of green tea extract on advanced glycation and cross-linking of tail tendon collagen in streptozotocin induced diabetic rats.
Food Chem Toxicol. 2007 Aug 15; Babu PV, Sabitha KE, Shyamaladevi CS. Department of Biochemistry, University of Madras, Guindy Campus, Chennai 600 025, India.
Diabetes leads to modification of collagen such as advanced glycation and cross-linking which play an important role in the pathogenesis of diabetes mellitus. We have investigated the effect of green tea extract on modification of collagen in streptozotocin induced diabetic rats. To investigate the therapeutic effect of green tea extract, treatment was begun six weeks after the onset of diabetes and green tea extract (300mg per kg body weight) was given orally for 4 weeks. The collagen content, extent of advanced glycation, advanced glycation end products (AGE) and cross-linking of tail tendon collagen were investigated. Green tea extract reduced the tail tendon collagen content which increased in diabetic rats. Accelerated advanced glycation and AGE in diabetic animals, as detected by Ehrlich's-positive material and collagen linked fluorescence respectively were reduced significantly by green tea extract. The present study reveals that green tea extract is effective in reducing the modification of tail tendon collagen in diabetic rats. Thus green tea extract may have a therapeutic effect in the treatment of glycation induced complications of diabetes.

Colon cancer benefit
Green tea extracts for the prevention of metachronous colorectal adenomas: a pilot study.
Cancer Epidemiol Biomarkers Prev. 2008 Nov; Shimizu M, Fukutomi Y, Ninomiya M, Nagura K, Kato T, Araki H, Suganuma M, Fujiki H, Moriwaki H. Department of Medicine, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu 501-1194, Japan.
Experimental studies indicate the chemopreventive properties of green tea extract (GTE) on colorectal cancer. Epidemiologically, green tea consumption of > 10 cups daily reduced colorectal cancer risk in Japanese. Because colorectal adenomas are the precursors to most sporadic colorectal cancers, we conducted a randomized trial to determine the preventive effect of GTE supplements on metachronous colorectal adenomas by raising green tea consumption in the target population from an average of 6 cups (1.5 g GTE) daily to > or = 10 cups equivalent (2.5 g GTE) by supplemental GTE tablets. We recruited 136 patients, removed their colorectal adenomas by endoscopic polypectomy, and 1 year later confirmed the clean colon (i.e., no polyp) at the second colonoscopy. The patients were then randomized into two groups while maintaining their lifestyle on green tea drinking: 71 patients supplemented with 1.5 g GTE per day for 12 months and 65 control patients without supplementation. Follow-up colonoscopy was conducted 12 months later in 125 patients (65 in the control group and 60 in the GTE group). The incidence of metachronous adenomas at the end-point colonoscopy was 31% (20 of 65) in the control group and 15% (9 of 60) in the GTE group. The size of relapsed adenomas was also smaller in the GTE group than in the control group. No serious adverse events occurred in the GTE group. GTE is an effective supplement for the chemoprevention of metachronous colorectal adenomas.

Is green tea extract thermogenic?
One study did not find green tea extract to have much of a thermogenesis effect, but caffeine did.

The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake.
Eur J Clin Nutr. 2007 Sep 19; 1Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark.
To investigate the effect of three different food ingredients tyrosine, green tea extract and caffeine on resting metabolic rate and haemodynamics, and on ad libitum energy intake (EI) and appetite. Twelve healthy, normal weight men participated in a four-way crossover, randomized, placebo-controlled, double-blind study. Treatments were administered as tablets of 50 mg caffeine, 500 mg green tea extract, 400 mg tyrosine, or placebo, and were separated by a 3-day washout. The acute thermogenic response was measured in a ventilated hood system for 4 h following ingestion. Blood pressure, heart rate (HR), and subjective appetite sensations were assessed hourly and ad libitum EI 4 h post-dose. Caffeine induced a thermogenic response of 6% above baseline value compared to placebo. The thermogenic responses to green tea extract and tyrosine were not significantly different from placebo. Tyrosine tended to increase 4-h respiratory quotient by 1% compared to placebo. Ad libitum EI was not significantly different between treatments but was reduced by 8%, 8% and 3% compared to placebo after intake of tyrosine, green tea extract, and caffeine, respectively. No significant difference in haemodynamics was observed between treatments. Only caffeine was thermogenic in the given dose and caused no haemodynamic side effects. The sample size was probably too small to detect any appetite suppressant properties of the treatments.